Process of dispersing fibrous material in a foam and resulting product



Nov. 7, 1961 F. sv WILCOX 3,007,840

PROCESS or DISPERSING FIBROUS MATERIAL IN A FOAM AND RESULTING PRODUCT Filed April 5, 195a Cross-sacfloncll illustration taken on line 5-5 of Flgl showing laminar arrangement of fibers nited States Patent Ofiice 3,007,840 Patented .Nov. 7, 19.61

This invention relates to a'novel ,process ofxforming nonwovenfibrous webs and improved products resulting therefrom.

In the makingof paper it isiwellknown to form aslurry .of.short fibers in water, run the fiber dispersion onto a porous screen, drain thetwater throughthe screen and a deposit a web of fibers thereon. Such processes arehasically the same since paper was first manufactured.

It has been. a-problem to form uniform water-laid webs from many synthetic fibers, particularlythose which are crimped or strongly hydrophobic, such as, e.g., glass,

\ polytetrafluoroethylene and various elastomeric fibers; also, all types of fibers having a relatively long length, i.e., greater than about A to /2 inch (depending. upon the denier and stiffness). Such' fibers agglomerate, ballup, and form large clumps when dispersed inwater .at fthe normal concentration used for paper nmaleing ie, .05% to .1% fiber and 99.95% .to99L9%: water.

The primary object of this invention is. theprovision of a process for and product of uniformtweb madefrom fibers or fibers and fibrids havinguproperties or physical shape which prevent the formation of :a uniform nonwoven web from an aqueous slurry-of'ithe fibrous mate'rial by prior art techniques. A: further objectis the provision of a uniform non-woven water-laid .webtalso know as a waterleaf) comprising strongly' -hydrophobic staple fibers, A still further object is: the provision-of uniform non-woven water-laid web comprising crimped fibers. A still further object is the provision of uniform non-woven, water-laid web comprising elastomeric staple fibers.

The above objects are accomplished by: forming a-dispersion comprising staple fibers in a foam-andrseparating a' non-Woven web therefrom by-depositing the foam, having the fibrous material dispersed therein, on ascreen =or-other porous substrate; whereby-the aqueous medium passes through the porous substrate anddeposits a-uniform web thereon. The resulting web is more uniform than those made heretofore from a dispersion -of the fibrous material in a continuous liquid phase. Furthermore, waterleaves deposited from foam-are not as laminar as those formed from dispersions in a continuous aqueous phase. The deposition of webs from a foam dispersion yields increased orientation of 'the' fibers 'perpendicular-to the plane "of the Web.

1 The term fibrids as used throughout the specification and claims is intended todesignate aheterogeneous mass of particles, the particles having .at least one dimension'of 10 microns r lessand of minor magnitude relative to its largest'dimension, ribbon-like portions of the fibrous matter among said particles being no greater than 100 microns in. width, said particles being non-rigid and smallenough to pass through a mesh screen, yet large enough so that 90% is retained by, a ZOO-mesh screen when deposited from an agitated dilute, suspensoid; said particles being-further characterized by a freeness number of between about 100 and 750 when in the form ofan aqueous slurry, and a capacity .to form a waterleaf.

. The polymericfibrids useful inthis invention are more 7 fully described in Vcopending U.S. application S.N. 635,876, filed January 23, 1957, byP.v W..Morgan, now

. inch long, .-which are self, elongatable .when heated. The above com- ,ponents-were subjected toagitation-for 30 seconds which .to a. foam. The foam .w th. the fibers ,drspersed therein was poured into a paper forming box having a screen in :order ofaddition for the components to-fornrthe dis- URE 4 is a @lanview of .a non-woven -the same fibers illustrated in FIGURE 3, the difference ;being the web wasformed from a dispersion of the in a foam. FIGURE 5 is a cross section illustration ataken ionline 5-5 of the non-woven web :illustrated in illustration and not limitation, the parts --..figures are given on a weight basis unless statedother- .tocover itwith. about 2 inches of Water.

.paper formingbox, a vacuum was applied which pulled .the water. and foam from the box and thefiberswereuni- -a length greater than about sir-able to add thefibers to the preformed foam. ,.It. is sometimes desirable to treat the fiberswith a foaming abandoned, and they maybe prepared in accordancewith .-the procedures set forth therein.

FIGURE 1 of the drawing is a plan view of a non- .woven web made from a conventional aqueous slurry of Mt inch, 3.5 denier-polyethylene terephthalate fibers dispersed in a continuous aqueous phase. FIGURE 2 ;is a plan view of a non-woven web made from/the .sarne Vfibers as illustrated in. FIGURE 1, the=,.diiference. .being the web was formed from a dispersion of fibersjin a foam instead of a continuous aqueous medium. FIGURES is a plan view of a non-woven web of inch, 4.75 denier crimped polyethylene terephthalate fibers deposited from a conventional aqueous dispersion of the fibers. FIG- web made. from FIGURE 1 of the drawing which shows the-planar or laminar arrangement of the fibers. FIGURE 6 is a cross-sectional illustration taken on line 6-6 of the nonwoven web illustrated in FIGURE 2 of the drawing which ,shows the three .dimensionalarrangement of the fibers.

The following specific examplesare given by way of and percentage wise.

, Example I To 1,000--parts-of waterwas added S parts 'of Triton 400 (octylphenyl polyglycol ether) and l/part of A 3.5 denier, polyethylene terephthalate ,fibers converted substantially all-the waterfrom a liquid-phase thebottom and containing sufiicient waterover the screen -As soon as the aqueous foam containing the fibers was poured into the formlydeposited on the screen in a three dimensional arrangement.

The wet Web was removed from the screen and dried. Thewebwas bulked by heating at 200 C. which caused the fibers to elongate an average of about"20% of their originallength. The web was extremely uniform, weighed .about 1.4 ounces per square yard and had a rating of +2 on arbitrary scale ranging from 2 to 2, where .zero represents a degree of uniformity which would be acceptable.

A web formed in like manner from a dispersion of the same fibers in the same amount of Water, but without the Triton foaming agent, had a rating of -1 in uniformity of fibers in the dry web. The dry web had considerable clumping of fibers as Wellas voidsin the web.

Generally,-in practicing this invention, inthecase of relatively short fibers, i.e., less than about inch, the

persion of thefibers-in the foam is not critical. The

Alternatively the-fibers In the caseof fibershaving .5 inch, it is generally decan be added to .the foam.

agent .before dispersing them in water. Incertain cases, it is advantageous to disperse the fibers, treatedwith foaming. agent, in :the. water. by .mild. agitation before Staple Example Type of Staple Fiber Denier Length,

inches Nylon 15.0 1% do 1 3.0 Polyethylene Terephthalate 0.1 tr, Grimped Polyethylene Terephthalate. 4. 75 yr (8-9 crimps per inch). Orimped polyethylene terephthalate 3.0 )4

(l6 crimps per inch). Polytetrafiuoro ethylene 6. la Crirnped Polyacrylonitrile (8-9 crimps 6. 0 9% per inch).

1 Polyhexamethylene adiparnide.

Example IX A foamed fiber dispersion having the following com- 7 position was prepared:

Parts by wt. Water 1000 Triton X-100 Polyethylene terephthalate fibers (self-elongatable when heated) same as Example I The above components were agitated for about 30 seconds. Substantially all the water was converted to foam and the fibers were dispersed throughout. The foamed fiber dispersion was transferred to a paper forming box having the screen covered with about 2 inches of water. As in the case of Example I, a vacuum was applied and a uniform web of fibers was deposited on the screen. The Wet web was removed from the screen and dried. The web was bulked by heating for 30 seconds at 200 used in the above Example X, aqueous dispersions of non fibrillated polymeric materials can be used as the binder for the fibers in the water-laid web, including elastomers, such as, e.g., copolymer of butadiene and acrylonitrile, neoprene and natural rubber; resinous materials, such as, e.g., terepolymers of acrylonitrile, methacrylic acid and butyl acrylate as well as the other terepolymers disclosed in U.S. Patent 2,787,603, plasticized polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride.

Useful products are also obtained when fillers, such as, e.g., silica, mica and various coloring materials, such as pigments, are dispersed in the foam along with the fibers in the above example.

Example XI The following composition was prepared:

' Parts by wt. Polyvinyl chloride (Geon 101) 5.0 Di(2 ethyl hexyl) phthalate 2.8 Pigments and fillers 2.0 Epoxidized soya bean oil (Paraplex G-62) 2.9 Methyl ethyl ketone 87.3

C. between platens which were just touching the web,

but no measurable pressure was applied by the platens. The dried web weighed about 4.3 ounces per square yard and had a rating +2 on the arbitrary scale for uniformity.

Example X A non-woven web was prepared from the following components:

Aqueous dispersion of .6 part of copolyester fibrids in 99.4 parts of water 25 The copolyester is the reaction product of sufficient ethylene glycol to combine with a mixture of 80 parts of terephthalic and 20 parts of isophthalic acids.

The above components were subjected to vigorous agitation to convert the water to a foam and disperse the fibers and copolyester fibrids throughout the foam.

A uniform non-Woven Web Was formed from the foamed fiber dispersion in the same manner as described for Example I. The copolyester fibrids were uniformly distributed throughout the web and the heating step caused them to bond to the fibers. The dried product had the appearance of a bonded web. [It was somewhat bulky and particularly suited for use as interliner between an outer and inner ply of garment. The final sheet contained about 5% copolyester binder and 95% fiber.

In place of the aqueous dispersion of the copolyester The above composition was prepared in the well known manner by grinding the pigments and fillers in the di(2 ethyl hexyl) phthalate and the epoxidized soya bean oil. The polyvinyl chloride was dissolved in the methyl ethyl ketone at about 60 C. The pigment-plasticizer mill base was thoroughly mixed in the polyvinyl chloride solution. One part of the polyvinyl chloride solution at about 60 C. was poured as a line stream into about 40-50 parts of water at about 25 C. while the water was vigorously agitated. Upon entering the turbulent water, the fine stream of pigmented and plasticized polyvinyl chloride was rapidly precipitated from solution as fibrids. The fibrids were well frazzled and of irregular shape. By means of a mesh screen, the fibrids were filtered from the mixture of Water and methyl ethyl ketone. While still on the screen, the fibrids were washed with water until substantially free of methyl ethyl ketone.

To 1,000 parts of water were added 2 parts of Triton X-100, 72 parts of the water wet fibrids (23.6 parts dry fibrids) and 4.4 grams of crimped polyethylene terephthalate fiber /2" long and 3.5 denier per filament having 8- crimps per inch. The water containing the foaming agent, fibers and fibrids was vigorous agitated to convert the water to a foam with the fibers and fibrids dispersed throughout. The foamed fiber-fiibrid dispersion was poured into a paper forming box while a vacuum was being applied to the bottom of the box. The fibrids and fibers were immediately deposited uniformly on the screen in the form of a web the fibers and fibrids being uniformly distributed amongst each other. The web was removed from the screen and dried. The dry web was pressed for 3 minutes at 350 F. at a pressure of about 75-100 pounds per square inch to fuse or weld the fibrids together Without destroying the fibrous character of the fibers.

The product was a fiber reinforced plastic sheet about 21 mils thick and weighing about 20 ounces per square yard. It was useful as an upholstery material.

Example XII A polytetrafluoroethylene gasket material was made in accordance with the following procedure.

A foam was prepared by agitating 2,000 par-ts of water and 4 parts of Triton X-100 foaming agent. To the foam was aded 32 parts of polytetrafluoroethylene fibers /8 inch long and 6.0 denier per filament, and 64 parts of water wet beaten polytetrafiuoroethylene fibers (46.0 parts dry). The above ingredients were vigorously agitated for about 1 minute to disperse'fibrous materials throughout the foam.

The'beaten polytetrafluoroe'thylene fibersca'n be prepared by forming asuspension or paste of polytetrafluoroethylene and extruding it in the formof-a filament rod or tube which is $43 to A" in diameter. During this operation, fibers are'formed in the extruded mateingp-thewebwas subjected to pressure of about '75 l pounds per square inch at 350Fffor 'minutes. :The pressed sheet was about 42 mils thick and weighed about 55.4 ounces per square yard.

The pressed sheet was ideally suited for use as a gasket material where resistance to high temperatures and corrosive chemicals is required.

The amount of fibrous material dispersed in the foam is not critical; usually, however, concentration ranging from .01 to 10% are particularly useful in practicing this invention. However, the length of fiber will control the preferred concentration depending upon the degree of uniformity required for the final product. In the case of short fibers, i.e., less than Mr inch in length, concentrations greater than 10% fiber in the foam are useful in carrying out this invention.

The type of foaming agent is not critical. Satisfactory results have been obtained by using proprietary products other than Triton Xl00, such as, e.g., Ivory soap chips; liquid foaming agents, such as, e.g., Joy and Lux; and solid foaming agents, such as Fab, Ad, and Tide. Any foam producing surface active agent, such as, for example, those disclosed in the book entitled Encyclopedia of Surface-Active Agents by J. P. Sisley et al., published 1952 by Chemical Publishing Company, Inc., can be used in carrying out this invention. The selection of the foaming agent Whether anionic, cationic or non-ionic for carrying out this invention is dependent upon its foam forming property. It will be obvious to those skilled in the art that the fluidity of the foam can vary over very wide limits, the only limitation being that the foam must be fluid enough to drain or be sucked through a screen fine enough to retain the fibrous materials. Best results are obtained when all the water is converted to foam.

It is to be understood that any of the conventional paper making machines can be used in practicing this invention, such as, e.g., Fourdrinier machines, continuous rotary paper making machines, or simple vacuum filters equipped with fabric, wool-felt or wire screen filters.

This invention is not limited to any particular type of fiber. Fibers other than those mentioned in the specific examples which are useful in carrying out the invention include various other synthetic fibers, such as, e.g., those derived from monochlortrifluoroethylene polymers, copolymers of tetrafiuoroethylene and hexafluoropropene, cellulose acetate, glass, asbestos and metals.

One of the outstanding advantages of the present invention is that it permits the formation of uniform waterlaid webs from staple fibers at least twice as long as those employed in conventional prior art paper making techniques. In the case of prior art conventional techniques, it has been diflicult and somewhat impractical to make uniform water-laid webs from fibers having a length greater than about .5 to .75 inch. In practicing this invention, there is no particular lower limit to fiber length, useful "products can .be "obtained from fibers as short as .01 inchin length. The upper limit :of fiber length isdependent upon'the denier (density) and stiffness of the fiber. Forexample, for a .1 denierfiber, 'thelength can beashighas to- /z' inch andfor l5 denier fiber, the length canbe1.5to.2."i) inches orhigher depending upon/the degree of agitation and type of agita- 'tion. The followingtable illustrates the preferred fiber length for the denier indicated:

Denier Fiber length, inches 0.5a Me Also thempresent invention;permits. the formation ,of uniform water-laid webs made from .crimped fibers,

go -awhich hasrnot rbeen possible bysprior arttechniques. :An-

other. outstandingadvantage is* that ,onlyz-a: fraction of the time required:for dispersing-fibers in liquid'water by, conventional processes is required in practicing this invention. A still further advantage is that much less water is required to disperse a given weight of fibers by the process of this invention than by prior art processes. Another outstanding advantage of the present invention is that it permits the formation of water-laid fibrous webs in which the fibrous materials are in a three dimensional arrangement, i.e., less planar or laminar than water-laid webs made by prior art techniques.

While there are above disclosed but a limited number of embodiments of the structure, process and product of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired there fore that only such limitations be imposed on the appended claims as are stated therein, or required by the prior art.

The embodiments of the invention in which an eX- clusive property or privlege is claimed are defined as follows:

1. The process which comprises forming a fluid dispersion of hydrophobic fibers at least about one quarter inch in length in a foam substantially free of a liquid phase and forming a nonwoven web from said dispersion.

2. The process of claim 1 in which the fibrous material comprises nylon.

3. The process of claim 1 in which the fibrous material comprises polyacrylonitrile.

4. The process of claim 1 in which the fibrous material comprises polyethylene terephthalate.

5. The process of claim 1 in which the fibrous material comprises crimped staple fibers.

6. The process of claim 1 in which said fibrous material comprises a fluorohydrocarbon polymer.

7. The process of claim 1 in which said fibrous material comprises a tetrafiuoroethylene polymer.

8. The process which comprises forming a fluid foam comprising water, a foaming agent and hydrophobic fibers at least about one quarter inch in length, said foam being substantially free of a liquid phase, and separating said fibrous material in the form of a web from said foam.

9. The process which comprises forming a fluid foam comprising water and a foaming agent, dispersing hydrophobic fibers at least about one quarter inch in length in said foam, said foam being substantially free of a liquid phase, applying said fiber containing foam to a porous medium, filtering said foam through said porous medium to deposit a web of said fibers thereon, and removing said web from said porous medium.

10. The process which comprises dispersing hydrophobic fibers at least about one quarter per inch in length in water in the presence of a foaming agent, foaming substantially all the water, and separating said fibers in the form of a web from said foam.

a non-fibrous particulate polymeric material in an aque-,,

ous foam substantially free-of a liquid phase, separating a non-woven web from said foam, heating said web at a temperature above the fusion temperature of said particulate material and below the fusion temperature of said fibrous material and pressing said web.

f polymeric material comprises a resinous material.

dispersing hydro- .1 4. The process which comprises 10 12. .The process of claim 11 in which the non-fibrous" phobic fibers at least about one quarter inch in length' and a non-fibrous particulate material in an aqueous foam substantially free of a liquid phase, and forming a -web from said foam.

15. The process which comprises forming a foamed fluid dispersion comprising hydrophobic fibers about one quarter inch in length and fibrids, said disper- 20 at least sion being substantially free of a liquid phase, and forming a non-Woven web from said dispersion.

References Cited in the file of this patent UNITED STATES PATENTS 1,740,280 Bryant Dec. 17, 1929 1,821,856 Spaiford Sept. 1, 1931 1,841,785 Bryant Jan. 19, 1932 1,870,279 Bryant Aug. 9, 1932 1,966,437 Bryant July 17, 1934 2,260,557 Burton Oct. 28, 1941 2,273,313 .Clapp Feb. 17, 1942 2,481,959 Wahlin Sept. 13, 1949 2,626,213 Novak Ian. 20, 1953 2,626,214 Osborne Jan. 20, 1953 2,730,479 Gibson Jan. 10, 1956 2,810,646 Wooding et al. Oct. 22, 1957 OTHER REFERENCES Casey: Pulp andPaper, Vol. I, Interscience Publishets, N.Y., 1952, page 364. 

1. THE PROCESS WHICH COMPRISES FORMING A FLUID DISPERSION OF HYDROPHOBIC FIBERS AT LEAST ABOUT ONE QUARTER INCH IN LENGTH IN A FOAM SUBSTANTIALLY FREE OF LIQUID PHASE AND FORMING A NON-WOVEN WEB FROM SAID DISPERSION. 